cpu/x86: Declare SMM_ASEG

This is really an inverse of SMM_TSEG to flag
platforms that should potentially move away
from ASEG implementation.

Change-Id: I3b9007c55c75a59a9e6acc0a0e701300f7d21f87
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34134
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/cpu/qemu-x86/Kconfig

@@ -22,3 +22,4 @@ config CPU_QEMU_X86
 	select SMP
 	select UDELAY_TSC
 	select C_ENVIRONMENT_BOOTBLOCK
+	select SMM_ASEG